Few biologically active materials are sufficiently stable so that they can be isolated, purified, and then stored in solution at room temperature. Typically, biological reagents are stored in a glycerol solution which is maintained at temperatures of 4° C., −20° C., or −70° C. They may be stored in bulk and then combined with other reagents before use.
In preparing reagents for convenient and efficient testing of biological samples, it is frequently important to obtain dry chemical blends in uniform, discreet amounts. One type of carrier or filler which has been used to stabilize biological reagents is glass-forming filler materials. The biological reagent solutions are incorporated into the glass-forming filler materials (which are water soluble or a water-swellable substance). They are then dried to produce a glassy composition which immobilizes and stabilizes the biological reagent. For examples of glass-forming filler materials for stabilizing biological reagents see U.S. Pat. Nos. 5,098,893; 5,200,399 and 5,240,843.
Carbohydrates such as glucose, sucrose, maltose or maltotriose are an important group of glass-forming substances. Other polyhydroxy compounds can be used such as carbohydrate derivatives like sorbitol and chemically modified carbohydrates. Another important class of glass-forming substances are synthetic polymers such as polyvinyl pyrrolidone, polyacrylamide, or polyethyleneimine.
Further examples of glass-forming substances include sugar copolymers such as those sold by GE Healthcare under the registered trademark FICOLL™. FICOLL™ has molecular weights of 5,000 to 1,000,000 and contains sucrose residues linked through ether bridges to bifunctional groups (U.S. Pat. No. 3,300,474). Such groups may be an alkylene of 2, 3 or more carbon atoms but not normally more than 10 carbon atoms. The bifunctional groups serve to connect sugar residues together. These polymers may, for example, be made by reaction of sugar with a halohydrin or bis-epoxy compound.
Stabilized biological materials in a glassy matrix of carbohydrate polymers, can be prepared, either by freeze-drying (Treml et al. U.S. Pat. No. 5,593,824; Franks and Hatley U.S. Pat. No. 5,098,893) or by vacuum drying (Walker et al. U.S. Pat. No. 5,565,318). These water-soluble reagents are convenient to use for complex molecular biology applications. This approach is particularly useful for reagent systems composed of enzymes, nucleotides and other components dispensed in single-use aliquots. Reconstitution of the glassy matrix delivers buffered enzymes for applications including DNA amplifications and DNA sequencing.
There are currently a number of dried molecular biology products on the market. However, some of these are made by a process that is rather cumbersome, and involves extensive manual work. Other products require refrigeration when dried. There is a need for an improved process for the generation of ambient temperature dried reagents.